Ferrous alloys and articles made therefrom



United States Patent O 3,163,525 FERROUS ALLOYS AND ARTICLES MADE THEREFROM Stewart G. Fletcher, Latrobe, and David P. Hughes, Liganier Township, Westmoreland County, Pa., assignors to Latrobe Steel Company, a corporation of Pennsylvania No Drawing. Filed Jan. 13, 1964, Ser. No. 337,133 8 Claims. ill. 75-126) This invention relates to ferrous alloys and in particular to ferrous alloys having resistance to notch sensitivity and other peculiarly advantageous properties for use in hot work applications in the forming of extremely hard and difficult to forge materials and in applications where dimension tolerance is important. This application is a continuation-in-part of our. application Serial No. 23,909, filed April 22, 1960, which in turn was a continuation-inpart of our application Serial No. 724,503, filed March 28, 1958, now Patent No. 2,949,356. There has long been a need for a steel capable of withstanding the stresses and wear problems encounteredin certain hot work applications, such as dies for forging extremely hard materials, as, for example, the superalloys used for high temperature service in jet engine parts, gas. turbine parts and the like. There has also been a need for an alloy capable ofrwithstanding the erosion encountered in extruding aluminum,

brass and magnesium, as well as in die casting and other hot work applications. The steels normally used for this service have a relatively short lifeand consequently the die expense per forged piece is high. Not only is die cost high in such applications but the lost time and labor involved in replacing dies is a very significant part of the cost of each part produced. The alloy of our Patent No. 2,949,356 solved the foregoing problems, however, it sometimes shows notch sensitivity at high hardness levels. When used in extremely severe die applications this notch sensitivity has shown a tendency to promote cracking in the dies toward the end of the die life.

We have discovered an alloy having not only the surprisingly advantageous properties for use in the applications for which the alloy of our Patent No. 2,949,356 was usable but which is free of the notch sensitivity which at times appears in that alloy. We have found an alloy which is deep hardening and non-deforming and will maintain its form and tolerance-dimensions underv the extreme conditions encountered in die forging the superalloys,=as well as extruding materials such as aluminum, brass and magnesium. We have also discovered that the alloy is relatively easy to form and yet has great impact strength, resistance to abrasion and therefore a long use life and resistanceto dimension change in use, as well as marked resistance to notch sensitivity.

We have found that the preferred composition of our alloy is C -L 0.75 V 2.5 Mn 0.4 Cr 5.25 Mo 1.1 Si 1.0

Balance substantially iron with residual impurities in ordinary amounts.

Patented Dec. 29, 1964 "Ice peculiar properties. The broader composition may fall within the limits of Balance substantially iron with residual impurities in ordinary amounts, in which alloy the vanadium shall appear in amounts within the foregoing limits that vanadium- 1 4.2

shall be with the limits 33% to 50%.

We have found that when the chromium or molybdenum concentration is in the lower end of the range set out above, it is preferable that the manganese concentration approach the upper end of the limits set out hereinabove in order that the resulting alloy have the most desirable properties. Themachining properties are varied by varying'the sulphur within the range set out hereinabove, the higher sulphur content promoting better machining as well as reducing the cost of forming dies for the various purposes to which this alloy may be applied. I

While we have given certain limits with respect to the concentration of tungsten and nickel which may be present, their presence is not necessary and in our preferred composition these elements are absent. However, their presence is optional and may be desirable for certain purposes within the ranges set out above. The carbon and vanadium are preferably maintained above about 0.6% and 2% respectively for best results.

. In order to illustrate the peculiar adaptability'of the present alloy for use as hot working dies for forging extremely hard and difficult materials, several dies were formed of the preferred composition. These dies were carbonused alongside dies made from conventional alloys as well as dies made from the alloy of our Patent No. 2,949,356. The dies were used to forge turbine blades from high alloy compositions, as, for example, Nimonic alloy. The dies were operated until a satisfactory product no longer could be obtained from the dies. It was found that the dies madeof the composition of the present invention and from the alloy made according to application Serial No. 524,503 produced about four times as many pieces as the conventional alloys. A die made of the alloy of the present invention produced somewhat fewer pieces than the die made from the alloy of our Patent No. 2,949,356 where notch sensitivitywas not a factor but produced more pieces where notch sensitivity became important. Other comparative tests of the same type using other high alloy materials showed a comparative life of four to ten times greater in dies made from the present alloy as compared with dies made from conventional alloys.

It is evident that the advantage of the present alloy as respects to die cost alone is very great. However, the true economic importance of this result becomes more apparent when it is realized that the cost in labor and lost time in changing dies is almost as great as the cost of the dies themselves so that an increase in die life of four times actually represents a saving of approximately eight times in over-all production costs. This is a very significant saving in the cost of producing high temperature super-alloy parts for turbines, jet engine parts and the like. 1

We have carried out tests comparing the notch sensitivity of pieces made from the alloy of our Patent No. 2,949,356 and pieces made from the alloy of this invention. V-notch Izod impact tests were conducted on these pieces after the pieces were austenitized at 1900" F. and tempered at 950, 1050, and 1150 F. The results appear in Table I.

Table I A t Alloy of No. 2,949,366 Alloy of this Appln.

Temper Temp. F.

Temp, F.

Im act Strength Impact Hardness Re Hardness Strength man- I Mn Si Or V M0 No. 2,949,356 This application The foregoing data shows the marked improvement in impact strength of the alloy of the present invention as compared with that of Patent No. 2,949,356.

While we have illustrated and described certain preferred embodiments of our invention, it will be understood that the invention may be otherwise embodied within the scope of the following claims.

We claim:

1. An alloy adapted for forming metals at high temperatures comprising about 0.6% to about 0.8% carbon, about 2% to not more than 2.9% vanadium, less than about 2% manganese, about 3.0% to about 8.0% chromium, up to about 2% tungsten, about 0.50%to 3.0% molybdenum, up to about 2% silicon, up to about 3% nickel, up to about 0.25% sulphur and the balance substantially iron with residual impurities in ordinary amounts in which alloy the vanadium appears in amounts within the foregoing limits such that the vanadium 1 4. 2

is within the limits of about 0.33% to about 0.50%.

2. An alloy adapted for hot working applications comprising about 0.75% carbon, about 2.5% vanadium, about 0.4% manganese, about 5.25% chromium, about 1.10% molybdenum, about 1.0% silicon and the balance substantially iron with residual impurities in ordinary amounts.

3. An article for forming metals at high temperatures formed from a steel alloy comprising about 0.6% to about 0.8% carbon, about 2% to not more than 2.9% vanadium, less than about 2% manganese, about 3% to about 8% chromium, up to about 2% tungsten, about 0.5% to 3% molybdenum, up to about 2% silicon, up to about 3% nickel, up to about 0.25% sulphur and the balance substantially iron with residual impurities in ordinary amounts in which alloy the vanadium appears in amounts within the foregoing limits such that the carbonvanadiurnl 4.2

carbontion at elevated temperatures, deep air hardening and reduced notch sensitivity.

4. A die formed from a steel alloy comprising about 0.6% to about 0.8% carbon, about 2% to not more than 2.9% vanadium, less than about 2% manganese, about 3% to about 8% chromium, up to about 2% tungsten, about .5 to 3% molybdenum, up to about 2% silicon, up to about 3% nickel, up to about 0.25 sulphur and the balance substantially iron withresidual impurities in ordinary amounts in which alloy the vanadium appears inamounts within the foregoing limits such that the vanadiuml 4.2 is within the limits of about 0.33% to about 0.50%, said die being characterized by high resistance to deformation at elevated temperatures, deep air hardening and reduced notch sensitivity.

5. -An article for forming metals at high temperatures formed from a steel alloy comprising about 0.75 carbon, about 2.5 vanadium, about 0.4% manganese, about 5.25% chromium, about 1.1% molybdenum, about 1% silicon and the balance substantially iron with residual impurities in ordinary amounts, said article being characte'rized by high resistance to deformation at elevated temperatur'es, deep air hardening and reduced notch sensitivity.

6. A die for forming metals at high temperatures formed from a steel alloy comprising about 0.75 carbon, about 2.5% vanadium, about 0.4% manganese, about 5.25% chromium,- about 1.1% molybdenum, about 1% silicon and the balance substantially iron with residual impurities in ordinary amounts, said die being character ized by high resistance to deformation at elevated temperatures, deep air hardening and reduced notch sensitivity.

7. An alloy adapted for forming metals 'at high temperatures comprising about 0.45% to about 0.8% carbon, about 1.5% to not more than 2.9% vanadium, less than about 2% manganese, about 3.0% to about 8.0% chrm mium, up to about 2% tungsten, about 0.50% to 3.0% molybdenum, up to about 2% silicon, up to about 3% nickel, up to about 0.25 sulphur and the balance substantially iron with residual impurities in ordinary amounts in which alloy the vanadium appears in amounts within the foregoing limits such that the Vanadium- 1 4.2 is within the limits of about 0.33% to about 0.50%.

8. An article for forming metals at high temperatures formed from a steel alloy comprising about 0.45% to about 0.8% carbon, about 1.5% to not more than 2.9% vanadium, less than about 2% manganese, about 3% to about 8% chromium, up to about 2% tungsten, about 0.5% to 3% molybdenum, up to about 2% silicon, up to about 3% nickel, up to about 0.25 sulphur and the balance substantially iron with residual impurities in ordinary amounts in which alloy the vanadium appears in amounts within the foregoing limits such that the vanadium 1 4.2

tion at elevated temperatures, deep air hardening and reduced notch s'ensiti'v1ty.

carbon carboncarbon- References Cited by the Examiner UNITED STATES PATENTS 2,575,219 11/51 Giles -126 DAVID L. RECK, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3, 163525 December 29 1964 Stewart G. Fletcher et 31, I

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2. line 30? after "properties" insert of the alloy --u Signed and sealed this 4th day of May 1965.

IEAL) Ltest:

IRNEST W. SWIDER I EDWARD J. BRENNER ttesting Officer Commissioner of Patents 

1. AN ALLOY ADAPTED FOR FORMING METALS AT HIGH TEMPERATURE COMPRISING ABOUT 0.6% TO ABOUT 0.8% CARBON, ABOUT 2% TO NOT MORE THAN 2.9% VANADIUM, LESS THAN ABOUT 2% MANGANESE, ABOUT 3.0% TO ABOUT 8.0% CHROMIUM, UP TO ABOUT 2% TUNGSTEN, ABOUT 0.50% TO 3.0% MOLYBDENUM, UP TO ABOUT 2% SILICON, UP TO ABOUT 3% NICKEL, UP TO ABOUT 0.25% SULPHUR AND THE BALANCE SUBSTANTIALLY IRON WITH RESIDUAL IMPURITIES IN ORDINARY AMOUNTS IN WHICH ALLOY THE VANADIUM APPEARS IN AMOUNTS WITHIN THE FOREGOING LIMITS SUCH THAT THE 